Objective: The purpose of this manuscript is to review the literature
concerning the alterations in the microvasculature in experimental hyp
ertension and aging. We also present new unpublished data and results
where previous studies have not addressed important questions. Methods
: The new studies were performed using a chronic cranial window to all
ow multiple observations of the cortical surface vasculature over time
. In vivo video, microscopic techniques were used to study long-term c
hanges in microvascular caliber (vasomotion). In some studies, a chron
ic, in-dwelling aortic catheter allowed chaotic analysis of short-term
blood pressure and heart rate variations. Results: In these new studi
es we demonstrated a reduction in number of small arteriolar endpoints
per cortical surface area in the spontaneously hypertensive rat and i
n the old Brown-Norway rat. There was also a reduction in the number o
f arteriole-to-arteriole anastomotic connections in the older rat, The
se vascular changes in the old rat were revised or prevented by calori
c restriction. In the old rat, there was also a reduction in the varia
bility of blood pressure, heart rate and microvessel caliber (vasomoti
on). Conclusions: These studies suggest that there is an alteration in
the morphology of the small arterioles in hypertension and aging, tha
t may lead to reduced ability to perfuse cortical tissue. In addition,
there appears to be a diminution of overall short-term cardiovascular
and microvascular control.